Help with LNK2019 problem

I'm getting an error when I try to compile the code and I do not know how to solve the problem. Please help! The assignment asks me to create a BOOLEAN function that can check if the graph is connected or not. So I decided to use DFS approach to this problem. But now my code does not want to compile please help. ERROR LNK 2019.

My code and other files necessary to run will be included in an attachment.

Error LNK2019 relates to the failure of the compiler to locate an external symbol referenced in a function (linker error). Is your rstream header file in the same folder as your CPP file?
Whats the full error message? Mind to post it here?